Penion maximus

Penion maximus is a species of very large predatory sea snail or whelk, commonly known as giant whelk or great whelk, a marine gastropod mollusc in the family Austrosiphonidae.

Description
Penion maximus is the largest species of Penion siphon whelk, and is endemic to Australia. The species could be confused with the sympatric species P. mandarinus, however P. mandarinus is typically smaller and has a smoother shell with a shorter siphonal canal. Their shells are highly coveted due to the intricate designs embedded in onto the shells.

Distribution
The range of the species extends from waters off Tasmania and Victoria to lower Queensland.

Evolution
Penion maximus is closely related to another Australian species P. mandarinus. The species have overlapping geographic ranges (sympatry) and may have evolved from a common ancestor via niche differentiation based on prey size and water depth.